Applied Science
Material Type:
Rice University
Provider Set:
OpenStax College
Amphiphilic, Antiporter, Aquaporin, Bulk Transport, Carrier Protein, Cell Recognition, Channel Protein, Co-transport, Concentration Gradient, Contractile Vacuole, Diffusion, Electrochemical Gradient, Endocytosis, Exocytosis, Facilitated Transport, Fluid Mosaic Model, Garth Nicholson, Glucose Transport Protein, Glycolipid, Glycoprotein, Hugh Davson, Hydrophilic, Hydrophilic Head, Hydrophobic, Hydrophobic Tail, Hypertonic, Hypotonic, Immunologist, Integral Protein, Integrin, Isotonic, James Danielli, Membrane Components, Membrane Fluidity, Membrane Function, Membrane Structure, Osmolarity, Osmoreceptor, Osmoregulation, Osmosis, Passive Transport, Peripheral Protein, Phagocytosis, Pinocytosis, Plasma Membrane, Potocytosis, Primary Active Transport, Rate of Diffusion, Recepter-mediated Endocytosis, S. J. Singer, Secondary Active Transport, Selective Permeability, Selectively Permeable, Sodium-potassium Pump, Solubility, Solute, Solvent, Solvent Density, Symporter, Tonicity, Transport Protein, Turgor Pressure, Uniporter
Creative Commons Attribution


This photo shows the hustle and bustle of Grand Central Station.
Despite its seeming hustle and bustle, Grand Central Station functions with a high level of organization: People and objects move from one location to another, they cross or are contained within certain boundaries, and they provide a constant flow as part of larger activity. Analogously, a plasma membrane’s functions involve movement within the cell and across boundaries' activities. (credit: modification of work by Randy Le’Moine)

The plasma membrane, the cell membrane, has many functions, but the most basic one is to define the cell's borders and keep the cell functional. The plasma membrane is selectively permeable. This means that the membrane allows some materials to freely enter or leave the cell, while other materials cannot move freely, but require a specialized structure, and occasionally, even energy investment for crossing.